Vehicle engines may be configured to operate using diesel fuels. Diesel fuel delivery and diesel fuel conditioning systems typically include a low pressure, or feed, pump functionally located with the fuel tank, and a high pressure pump functionally located relatively spaced from the fuel tank. There is also, typically, at least one fuel filter arranged to filter out particles which may be in the diesel fuel. It is common to locate the fuel filter downstream of the fuel pump. However, this creates the disadvantage in that “dirty” fuel may be passed through the pump. One such example is disclosed in U.S. Pat. No. 7,793,642 to Yonemoto et al.
JP 2003-176761 discloses an alternative wherein a fuel filter is located on the upstream side of the low pressure pump. However this arrangement includes the common shortcoming in that the filter is located within the fuel tank thereby requiring the tank to be emptied, and drained, before the filter can be extracted from the fuel tank for cleaning or replacement and the like. It is also common that downstream filters be located inside the fuel tank. This, of course, also requires draining and opening of the tank for removal and/or replacement of the filter.
The inventors have recognized several potential issues with these approaches. For example, downstream filters do not protect the pump adequately. Is addition, a great many pump warranty claims are caused by plugged filters. Many times when a filter is clogged, the whole Diesel Fuel Conditioning Module (DFCM) is replaced rather than the just the filter. This, of course, is more expensive than warranted.
Various embodiments may be configured to provide a diesel fuel conditioning system for a diesel engine which may include a fuel pump located within a fuel tank configured to pump fuel to the diesel engine, and a fuel filter located outside of the fuel tank operatively located upstream in a flow of fuel from the fuel pump. In this way the fuel pump may be protected from particles in the fuel; fuel filter replacement may be easier; and may result in lower warranty cost.
Various embodiments may also be configured to provide a diesel fuel conditioning system for a diesel engine which may include a fuel tank, a fuel filter located outside of the fuel tank; and a vacuum chamber coupled with a pressure chamber via a fuel pump located within the fuel tank. The fuel pump may be configured to pull fuel from the fuel tank through the fuel filter and into the vacuum chamber. In this way various embodiments may provide an in-tank pump that may be configured to suck fuel through the externally mounted filter and back to the tank reservoir. This may allow the dirty fuel in the tank to pass through a standard filter or a customized filter that may be capable of reducing debris down to, for example, 10 microns or less before entering the pump.
Another issue the inventors have recognized is that low pressure pumps may sometimes cause vibrations which may create excess noise and/or mechanical fatigue in the system. Embodiments in accordance with the current disclosure may include a pressure chamber that may be is used to dampen vibration of the pump's pressure spikes.
The pressure chamber may also provide a mechanism to separate the air at the tank. The mechanism to separate the air may include an air bleed valve configured to allow air to escape from the pressure chamber, and therefore from the fuel stream, before being directed to the engine.
Yet another issue that various embodiments may be configured to address is the presence water in the fuel which may otherwise be emulsified by the action of the pump. Emulsified water is undesirable in that it may be passed to the engine combustion chamber in the fuel. The external filter in accordance with the current disclosure may include a water separation reservoir configured to capture water separated from the fuel, as the fuel passes through the filter, before the fuel passes through the pump.
Another issue with diesel fuel filters, in particular at low ambient temperatures, such as during an engine cold-start, is that wax may precipitate out of the diesel fuel. The precipitated wax may clog a fuel filter while also reducing the fluidity of the fuel. The amount of wax that precipitates from the fuel may depend upon the fuel properties and ambient temperature the vehicle is started in. As such, the precipitated wax in the fuel reduces the pressure of the low pressure fuel system and performance of the high pressure fuel system and, if severe enough, can cause damage to the fuel system. Various embodiments may provide a fuel recirculation valve configured to selectively direct at least of portion of fuel returned from the engine to the filter. In this way fuel heated by being passed through portions of the engine, i.e. through an engine fuel rail, may be selectively passed through the filter in order to melt wax that may have accumulated in the filter.
In one example, some of the above issues may be addressed by a method for a fuel conditioning module of a diesel engine including directing fuel from inside of the fuel tank through a fuel filter located outside of the fuel tank into a vacuum chamber positioned inside the fuel tank, before directing the fuel to the diesel engine.
In one example the method for a fuel conditioning module of a diesel engine may include configuring the pump to form a vacuum in the vacuum chamber in order to draw fuel from the filter into the vacuum chamber. The method may also include directing fuel from the vacuum chamber into a pressure chamber and then directing the fuel from the pressure chamber to the diesel engine.
In another example the method for a fuel conditioning module of a diesel engine may include locating the fuel filter outside of the fuel tank in a vertically mounted configuration and allowing for removing and replacing the fuel filter with a similarly configured fuel filter without opening the fuel tank, or disengaging the fuel tank from an engine compartment.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.